Gain-clamped Erbium-doped Fiber Amplifier Research Articles

Comparison between regenerative-feedback and cofeedback gain-clamped EDFA

The erbium-doped fiber amplifier (EDFA) with regenerative feedback is compared with the cofeedback scheme. Without the bandpass filter, the injected signal experiences regenerative amplification and results in a higher signal gain. Such an above-threshold regenerative amplifier also exhibits a lower noise figure due to a higher inversion for the transition corresponding to the signal wavelength of 1550 nm. A near quantum-limited noise figure of 3.1 dB is achieved at the maximum pump power of 134.5 mW, showing nearly complete inversion at the EDF input end in the regenerative-feedback scheme. A low (<10/sup -10/) bit-error rate has been achieved with saturation input signal power above -12 dBm.

Lasing wavelength dependence of gain-clamped EDFA performance with different optical feedback schemes

Performance of gain-clamped erbium-doped fibre amplifier with different optical feedback schemes has been studied as a function of lasing wavelength. An inverse relation of the signal gains with the amplified spontaneous emission spectrum is observed for the entire laser tuning range as a result of the population variation caused by the different strength of the oscillating laser. The noise figure also shows a feature of the lasing wavelength dependence. However, co-feedback scheme exhibits behaviour opposite to that of the counter-feedback.

Optically gain-clamped wideband erbium-doped fiber amplifier using a common figure-eight feedback-loop lasing light

We propose an optically C plus L-band (1530–1600 nm) silica-based wideband gain-clamped (GC) erbium-doped fiber amplifier (EDFA) using a common figure-eight feedback-loop lasing light at 1568 nm, which is just located within the dead-zone between the C- and L-bands, where no WDM channels can be transmitted. The optical gain and noise figure characteristics of this wideband GC–EDFA in terms of the loop attenuation are examined. This wideband GC–EDFA may find important applications in broadband DWDM networks.

A gain‐clamped erbium‐doped fiber amplifier (GC–EDFA) for WDM optical packet‐switching system

AbstractThe use of a dual‐stage gain‐clamped erbium‐doped fiber amplifier (GC–EDFA) having a pump laser diode and 16‐channel wavelength‐division multiplexing (WDM) with 0.8 nm spacing in the C‐band of 1545–1560 nm wavelength was demonstrated in a burst packet‐mode optical switching system through an experimental setup. © 2002 John Wiley &amp; Sons, Inc. Microwave Opt Technol Lett 32: 167–170, 2002.

All-optical gain-clamped erbium-doped fiber-ring lasing amplifier with laser filtering technique

A unique laser filtering technique of a gain-clamped erbium-doped fiber amplifier based on ring-laser cavity is demonstrated. The filtering mechanism is achieved using a single fiber Bragg-grating, which also functions as a laser feedback reflector at the output end of the amplifier. This new design has low noise and most important, shows up to 98% reduction in output laser intensity as compared with a previous design studied earlier. An optimum result with gain and noise around 25 and 3.5 dB, respectively, obtained for a dynamic range of input signal power up to -8 dBm.

Gain‐clamped erbium‐doped fiber amplifier using a single fiber Bragg grating

A new design of an all-optical gain-clamped erbium-doped fiber amplifier is demonstrated. The amplifier is based on the conventional ring cavity, where the gain is clamped at 21.84 dB via optical feedback using a single fiber Bragg grating for an input signal power as high as −8 dBm. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 290–293, 2001.

Beat phenomena in cascaded all optical gain-clamped erbium-doped fibre amplifiers

Analytical expressions and the basic rules of beat phenomena in cascaded gain-clamped EDFAs with ring cavity lasing structures during channel addition/drop are obtained and verified experimentally. Methods to suppress beat phenomena are also proposed.

Theoretical analysis of spectral hole burning and relaxation oscillation in all-optical gain stabilized multichannel erbium-doped fiber amplifier (EDFA)

The spectral hole burning effects and gain dynamics of all-optical gain clamped multichannel erbium-doped fiber amplifiers (EDFAs) are modeled. The two-level laser model is used to write the propagation and rate equations of the inhomogeneous laser medium. The governing equations are an uncountable system of partial differential equations (PDEs). After some mathematical manipulations, averaging over the fiber length and introducing an approximation method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The gain dynamics and hole burning of an all-optical stabilized multiwavelength EDFA and the transient response of an optical fiber inverter are analyzed by the solution of the system of ODEs. Theoretical results are in good agreement with the published experimental result.

Modeling and optimization of add–drop dynamics in gain-clamped fiber amplifiers

A new dynamic model for gain-clamped fiber amplifiers is presented. The model can simulate the transient behavior of a gain-clamped erbium-doped fiber amplifier as a function of its controlling parameters. Results show the detailed dependence of the amplifier gain dynamics on launched pump power and reveal the pump-power penalty incurred in implementing gain control with minimal transients to power disturbances. The effect on the transients of varying the laser cavity feedback coupling is also presented. Model accuracy is verified by the excellent quantitative agreement with dynamic measurements over a range of operating conditions. Results show how an increase in pump power can effectively suppress both the dynamic and the steady-state signal power transients in wavelength-division multiplexing channel add-drop operations.

Gain-clamped erbium-doped fibre amplifier for wavelength division multiplexed systems

Abstract Amplification of multiwavelength signals by an erbium-doped fibre amplifier (EDFA) is becoming critical, due to the proliferation of wavelength division multiplexed systems. However, when a standard EDFA is employed, dissimilarities between signal gains may prove unacceptable. Thus, a novel gain-clamped EDFA is proposed here to tackle the issue of gain tilt, a measure of maximum gain difference. The suitability of the configuration is then investigated through a numerical model, which is developed based on the standard EDFA and fibre laser models.

A Novel Gain-Clamped Erbium Doped Fiber Amplifier for Wavelength Division Multiplexed Systems

Amplification of multiwavelength signals by an erbium-doped fiber amplifier (EDFA) is becoming critical, due to the proliferation of wavelength division multiplexed systems. However, when a standard EDFA is employed, the dissimilarities among the signals’ gain may prove unacceptable. Thus, a novel gain-clamped EDFA is proposed here to tackle the issue of gain tilt. The suitability of the configuration is then investigated through a numerical model, which is developed based on the standard EDFA and fiber laser models.

Gain-clamped erbium-doped fibre amplifier for wavelength division multiplexed systems

Amplification of multiwavelength signals by an erbium-doped fibre amplifier (EDFA) is becoming critical, due to the proliferation of wavelength division multiplexed systems. However, when a standard EDFA is employed, dissimilarities between signal gains may prove unacceptable. Thus, a novel gain-clamped EDFA is proposed here to tackle the issue of gain tilt, a measure of maximum gain difference. The suitability of the configuration is then investigated through a numerical model, which is developed based on the standard EDFA and fibre laser models.

A novel compensating light injection configuration for gain-clamped EDFA's

A novel compensating light injection configuration for gain-clamped erbium-doped fiber amplifier (EDFA's) is proposed. The compensating light is backward injected from the end of the first stage of the amplifier and then reflected by a grating at the amplifier input end. Very wide input dynamic range (0.5 /spl mu/W-500 /spl mu/W) with less than 1 mW of compensating light and low noise penalty (<0.5 dB) is demonstrated.

Gain stabilization in gain clamped EDFA cascades fed by WDM burst-mode packet traffic

This paper studies via simulation the stabilizing effect of all-optical gain-clamping (AOGC) in a chain of erbium-doped fiber amplifiers (EDFA) fed by wavelength-division multiplexing (WDM) burst-mode packet traffic. AOGC is necessary to suppress swings of output power and optical signal-to-noise ratio (OSNR). A case study is selected, in which only the first EDFA in a cascade of six amplifiers is clamped using a ring laser configuration. A numerical model which solves the transcendental equation for the average inversion at each EDFA is used for the analysis. The traffic is generated on the eight WDM channels by ON-OFF time-slotted sources, with statistically independent ON and OFF durations, randomly generated by a truncated Pareto distribution with infinite variance. The simulation model includes the generation of amplified spontaneous emission within each amplifier and the propagation of the lasing power generated in the AOGC EDFA through the cascade. It is shown that the sizable power and OSNR swings arising in an unclamped cascade of EDFA's can be effectively suppressed when a lasing signal a few decibels above the aggregate signal power develops in the AOGC EDFA and propagates along the cascade.

Eight‐channel WDM amplification in a gain‐clamped fiber amplifier

A gain-clamped erbium-doped fiber amplifier (EDFA) is demonstrated using a double-pass superfluorescent laser centered in the 1530 nm band. The gain is clamped at 21 dB with about 0.2 dB variation, and the gain flatness between channels is kept below 0.6 dB over 11 dB of input signal power variation. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 56–57, 2000.

An analytical formulation of the transient response of gain-clamped EDFA's

A small-signal analytical model describing transients within a gain-clamped erbium-doped fiber amplifier is presented. The model gives an accurate description of the relaxation oscillations experienced by surviving channels when there are small input variations to the amplifier. The model also provides good approximations for medium input variations, conditional on the amplifier being highly saturated by the gain-clamping lasing signal. This is demonstrated by agreement between our analytical model and numerical simulations.

Simple dynamic model of all-optical gain-clamped erbium-doped fiber amplifiers

A simple dynamic model of laser-gain clamped erbium-doped fiber amplifiers (EDFAs) using ordinary differential equations is presented. The model not only provides a fast means of calculating EDFA gain dynamics, but also shows explicitly how the laser relaxation oscillation frequency and damping constant are affected by design parameters through analytical expressions. It is shown that the dynamic power excursion caused by relaxation oscillations can be reduced by increasing the oscillation frequency. The simplified model has two limitations: first, the amplified spontaneous emission (ASE) spectrum is not fully resolved and the noise figure can not be studied; second, the effect of spectral hole burning, which also causes gain excursion, can not be modeled. The first limitation can be removed by ASE-resolved modeling, where the concept of average inversion is also utilized to save computing time.

Gain spectrum equalization of all-optical gain-clamped erbium-doped fiber amplifier

We experimentally investigate the gain spectrum of erbium-doped fiber amplifiers whose gain is clamped by internal laser oscillation. The gain is ideally clamped and immune to the input signal power in the wavelength range of 17 nm. The clamped gain spectrum is equalized by a Mach-Zehnder interferometer, and we achieve the 17-nm-wide uniform gain, which is not dependent on input optical power levels.

Small signal modulation responses of gain-clamped erbium-doped fibre amplifiers

The small signal modulation and intermodulation responses of the gain-clamped erbium-doped fibre amplifier were investigated experimentally for the first time. Around the relaxation oscillation frequency, a strong resonance dip and peak were observed in the modulation and intermodulation characteristics, respectively.

Noise figure improvement of optical gain-clamped fibre amplifier by mid-point band reject filter for lasing light

A new configuration for improving the noise performance of an optical gain-clamped erbium-doped fibre amplifier is proposed. The effect is also demonstrated by experimentally comparing the noise figure of the proposed configuration to that of the previously proposed configuration.